Yes, quite normal to drive across Europe like that - I've done it by car towing my boat several times. France has excellent roads and generous speed limits, so with two drivers you can do it overnight if you keep your foot down. It's why GT cars came about - big Astons, Bentleys and Jaguar coupes designed to get their wealthy owners to their yacht on the Rivera or villa in the Alps.

Regarding ferry or train - my guess would be ferry as there's no restaurants or duty free shops on the train. The ferry is slower but cheaper - and I expect a lot cheaper for a bus given that the ferry companies would love to see all those passengers spending money on board.